There is a problem in a process of manufacturing a semiconductor device (e.g., a micro-electro mechanical system (MEMS) device) using certain, atypical metals for which no established plasma etch chemistry exists, because removing residual metal from a metal layer during metal patterning may require a lift-off technique. For example, a microbolometer infrared (IR) imager with a focal plane array of individual bolometers may include a number of such metals, for example vanadium oxide or VOx (used as the active material sensitive to the desired IR frequency), vanadium, titanium, NiCr, and or a Ti—NiCr stack. Further complicating matters, these metals may require sputtering for deposition—a method of deposition which has been considered unsuitable for lift-off processing. The unsuitability stems from residual metal artifacts that may remain on an edge of the device pattern, which may result in electrical shorts and reduced device yields.
Lift-off may be performed by immersing the wafers in a solvent bath to dissolve the patterned resist and manually swabbing the wafers to remove any residual metal flaps. This process is thought to be undesirably inefficient for mass production and incompatible with Class 1 conditions and operations of a chip manufacturing facility.
As a result, there is a need for an automated lift-off and metal flap removal method which will remove metal from non-pattern areas and remove metal flaps at the edges of patterned areas without damaging the device (e.g., microbolometer IR imager).